Everyone from medical experts to casual sports fans have heard the term muscle memory. It’s often brought up in the context of a trained athlete or fitness enthusiast having time off from physical activity due to an injury, scheduled rest, or off-season. Everyone understands that an athlete (or former athlete) who is currently out of shape will recover his or her physical abilities much faster than a relatively untrained person.
“He has the muscle memory to make a quick come-back.”
We assume that high performers recover from injuries so quickly and completely because they have nearly constant and free access to physicians, rehab specialists, nutritionists, trainers, and all the latest equipment. These are all good. But honestly, the primary reason why the elites recover so well has less do to with the providers around them and much more to do with the athlete. It is the accumulated years of brain development that truly makes for fast physical recovery.
So in this sense, muscle memory is absolutely…REAL.
But how do muscles remember? Go ahead and speak to a muscle directly. Whisper to a calf or play Morse code on a bicep. Better yet, stick electrodes into or on top of a muscle and speak to it through electrical stimulation. Ask a muscle to do anything more than contract (shorten its length), and it will only sit there all jacked, staring blankly at you.
Motor memory is muscle memory’s slightly less cool but more technically correct cousin. The key player in motor memory is, of course, the brain and the manner in which it utilizes the nervous system.
And yet, the brain can’t do a darn thing for itself. But it’s great at shooting orders!
What exactly does the brain “remember?”
1. Desire. First of all, trained people often want to regain their physical abilities. They have experienced what life feels like as a physically able, solid force of a person and have great motivation to avoid the alternative. Even recreational athletes usually have much more desire than the typical person to do whatever it takes to regain their physical abilities to the greatest extent possible.
2. Previously trained brains have learned to be smart about discomfort. They willingly push into misery, even embrace it, because they realize the triple pay off. They know that “no pain, no gain” is a half truth, and can easily discriminate between physical damage and beneficial discomfort.
3. The brain remembers the circuitry of skilled movement. Riding a bike is, well, like riding a bike. The neurological motor plans of lifting, running, jumping, throwing, etc, last much longer than the actual physical ability to perform them. Deconditioned athletes reap the rewards of having worked through thousands or tens of thousands of well executed repetitions in the past. The body may be soft and weak, but the brain did not forget.
4. On the more technical side, through consistent and regular training, the brain learns how to signal the muscles more efficiently. Through rate coding (bundling nerve signals in the most efficient manner), motor unit synchronization (getting various muscles and parts of muscles on the same page and working together), and reciprocal inhibition (getting opposing muscles to relax and contribute through improved stabilization), the brain literally knows how to get more out of whatever strength and flexibility that the body currently possesses.
Warning: The reasons why former athletes and fit people recover quicker are the exact same mechanisms by which they can easily over-do it and make themselves VERY sore when returning to training after time off. The brain can “tell” the body to do far more than the muscles and joints are ready for. Delayed Onset Muscle Soreness is also very real!
5. The nucleus is said to be the “Brains” of each cell in our body. When a muscle is exercised, nuclei are added, and they’re not lost when you we stop exercise and the muscles atrophy. Some scientists think this is an additional reason why previously trained people do bounce back more rapidly than untrained folks. So after all, in this regard, previously trained muscles do have better memory.
In summary, muscle memory is not Bro-Science. It’s mostly a brain skill, earned through years in the training trenches, that’s not easily erased by a little time off. Go out and get you some!
Bonus: Muscle memory can be “built” quicker and forged to a greater extent by becoming powerful and efficient in a few basic free weight exercises, as opposed to using machines for strength or changing your program every other week. Muscle confusion is sooo 2007, so work those functional movement patterns. 
Bonny Lane Club 